The development of semiconductor devices is always walking toward higher density and higher frequency. Conventionally, a probe card is mounted on the test head of a tester for chip probing semiconductor devices in wafer form. In order to save the testing cost and to increase the testing throughput, multiple DUT (device under test) probing is required and developed. For multiple DUT probing, the circuit design of a probe card becomes more complicated than ever. Moreover, the EMI (Electro-Magnetic Interference) will become a dominant factor in high frequency probing. Without accurate EMI control in a probe card, the testing results may be misleading and causing yields loss.
A probe card assembly had been disclosed in the U.S. Pat. No. 5,491,426. A plurality of probe needles are installed on the lower surface of a probe card. A decoupling apparatus is installed in a cavity of a load board on the upper surface of the probe card to eliminate signal noises causing by electromagnetic waves. Nevertheless, the decoupling apparatus can filter out only the signal noise generated by the cables connecting between a tester and a probe card, but not the signal noise generated by the probe card itself. The decoupling apparatus does not function effectively in this case and only can fit for the conventional cantilever probe cards.